Biology subjects

Mizubuti, E. S. G.

Publications and source records attributed to Mizubuti, E. S. G..

4 recordsLinked to original sources

bioRxiv2022

A shift in the pathotype diversity and complexity of Phytophthora sojae, causal agent of root and stem rot of soybean, in Brazil

Soybean root rot disease caused by the oomycete Phytophthora sojae is particularly destructive, once it is a host-specific pathogen that can infect and kill soybean plants at any stage of growth. The use of resistant cultivars is the most effective method of controlling the disease. Therefore, monitoring changes in the adaptability of P. sojae population to resistance genes (Rps) is extremely important not only from an epidemiological point of view but mainly for the management of the disease and durability of the Rps genes. We investigated the pathotypes of 40 isolates of P. sojae, sampled from the region with a higher incidence of soybean root rot in Brazil, using a set of 14 soybean differentials. The first study investigating pathotype diversity in Brazil was published in 2013. A decade later, we are reporting a major shift in pathotype diversity and complexity. This information can be useful for breeding programs aiming at developing soybean cultivars with resistance to root and stem rot and optimize the usage of genes and germplasm.

microbiology↗

bioRxiv2022

The Brazilian population of Fusarium oxysporum f. sp. cubense is not structured by VCG or by geographic origin

Fusarium wilt, caused by the soil-borne fungus Fusarium oxysporum f. sp. cubense (Foc), is considered one of the most destructive diseases of bananas. Paradoxically, knowledge of the genetics of the pathogen population in the Americas is very limited. In this study, a collection of 178 monosporic isolates from several banana producing regions, located in different climatic zones along a South to North transect in Brazil, was formed to assess the genetic structure of the population of Foc. The isolates underwent pathogenicity tests, PCR diagnosis for the detection of Tropical race 4 and screening to SIX homologs. The VCG of 119 isolates was determined by pairing against 17 testers. A group of 158 isolates was selected for microsatellite genotyping. There was moderate diversity of Foc in Brazil. Eight VCGs were identified: 0120, 0122, 0124, 0125, 0128, 01215, 01220, and 01222, of which 78% of isolates belong to a single VCG, while 22% of isolates belong to complexes of VCGs. The distribution of VCGs is uneven and independent of the banana genotype. VCGs were correlated with homologs of the SIX genes and varied according to geographic regions. Four SSR loci were polymorphic and on average 7.5 alleles were detected per locus. Thirty-five multilocus genotypes (MLGs) were identified. There was no association between VCG and MLGs and no genetic structure of the population of Foc in Brazil was detected.

microbiology↗

bioRxiv2021

On the assessment of the sources of inoculum of bacterial wilt in Brazil.

Dispersal of Ralstonia spp. cells by water and contaminated plant material and the importance of weeds as inoculum sources have been poorly investigated. Water of rivers, soil from fields of diverse crops and areas of natural vegetation both from the Amazonia, Cerrado and Mata Atlantica biomes, besides soil of the rhizosphere of weeds present in tomato fields with records of bacterial wilt were sampled and analyzed to detect Ralstonia spp. Seeds of tomato plants artificially and naturally infected with Ralstonia spp. were also processed. All samples were enriched a priori in selective medium South Africa (SMSA) and colonies were isolated in plates containing solid SMSA. Detection of Ralstonia spp. was confirmed by polymerase chain reaction with specific primers. The Co - operational PCR (CO-PCR) was also used to detect Ralstonia spp. Colonies were obtained from soil samples and from a commercial substrate sample. Five soil samples from eggplant fields, one from coffee field, one substrate from potato seed tuber production, two soil samples from the rhizosphere of Amaranthus spp., one from Bidens pilosa and one from Solanum americanum tested positive for Ralstonia spp. Besides these soil samples, five water samples of rivers were positive for CO-PCR detection: two samples from Amazonia, one from Cerrado and two samples from irrigation water collected from tomato fields located in the Mata Atlantica biome. Ralstonia spp. were not detected in tomato seeds. These results revealed potential inoculum sources, especially weeds, in areas with historical records of bacterial wilt. Additionally, rivers may act as dispersal agents of inoculum of Ralstonia spp.

ecology↗

bioRxiv2021

Weevil borers affect the spatio-temporal dynamics of banana Fusarium wilt

Dispersal of propagules of a pathogen has remarkable effects on the development of epidemics. Previous studies suggested that insect pests play a role in the development of Fusarium wilt (FW) epidemics in banana fields. We provided complementary evidence for the involvement of two insect pests of banana, the weevil borer (Cosmopolites sordidus L. - WB) and the false weevil borer (Metamasius hemipterus L. - FWB), in the dispersal of Fusarium oxysporum f. sp. cubense (Foc) using a comparative epidemiology approach under field conditions. Two banana plots located in a field with historical records of FW epidemics were used, one was managed with Beauveria bassiana to reduce the population of weevils, and the other was left without B. bassiana applications. The number of WB and FWB was monitored biweekly and the FW incidence was quantified bimonthly during two years. The population of WB and the incidence (6.7%) of FW in the plot managed with B. bassiana were lower than in the plot left unmanaged (13%). The monomolecular model best fitted the FW disease progress data and, as expected, the average estimated disease progress rate was lower in the plot managed with the entomopathogenic fungus (r = 0.0024) compared to the unmanaged plot (r = 0.0056). Aggregation of FW was higher in the field with WB management. WB affected the spatial and temporal dynamics of FW epidemics under field conditions and brought evidence that managing the insects may reduce FW of bananas intensity.

systems biology↗